﻿using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;

namespace VirtualRink.Library
{

	public static class PredicateBuilder
	{
		public static Expression<Func<T, bool>> True<T>() { return f => true; }
		public static Expression<Func<T, bool>> False<T>() { return f => false; }

		public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
															Expression<Func<T, bool>> expr2)
		{
			var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
			return Expression.Lambda<Func<T, bool>>
				  (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
		}

		public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
															 Expression<Func<T, bool>> expr2)
		{
			var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
			return Expression.Lambda<Func<T, bool>>
				  (Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
		}
	}
}